CBR1000RR Engine Build Part 1
I am in the middle of building an engine for a CBR1000RR track bike and I thought I’d document the build here. The engine came in fitted to the bike and was completely standard except for a Nova gearbox that had been previously fitted. The customer provided some parts (JE high compression pistons, HRC cams, HRC adjustable cam timing wheels, HRC valve springs and HRC base and head gaskets) and asked for a moderate level of tune to enable longer rebuild intervals for the engine rather than an outright power gain and more regular rebuild intervals. After stripping the engine, washing all parts and checking everything for wear it was time to start the build. All internal parts were within tolerances and no wear or damage was visible so not many parts required changing, only the main bearing shells, big end bearing shells, con rod bolts, crankcase stretch bolts, gaskets and the JE pistons and HRC parts.
My first step was to tackle the cylinder head. The cylinder head’s face was perfectly straight and due to high compression pistons being fitted the decision was made not to machine any material off as this would raise compression too much. This left the ports and combustion chamber to work on. Without going into too much detail I reshaped the ports slightly and finished the surfaces in a different way for the inlet and exhaust ports (this is to do with how I want the air/fuel mixture to travel in the inlet port and the exhaust gas to travel in the exhaust port). The rough finish of the combustion chambers were smoothed slightly and polished. As the customer had asked for some light head work I kept port and combustion chamber modification to a minimum. With each valve cleaned up and still paired to it’s original valve seat, engineers blue was used to check the valve seating area was still within tolerance and then it was time to assemble the valves, collars, springs and collets in the head.
With the head finished for now, next up was the bottom end. With the gearbox installed back in the crankcase, main and big end bearing shell sizes were selected to give the optimum clearance allowing for the least amount of friction. Pistons and con rods were weighed and paired up so each pair had the same mass. Piston to cylinder clearance and piston ring end gaps were measured before assembling the pistons, con rods, cylinder, crank and crank cases together.